Remove a deleted file from libjingle.gyp
Remove a deleted file from libjingle.gyp

source/talk/app/webrtc/webrtcsessionobserver.h was removed in http://code.google.com/p/libjingle/source/detail?r=129 , rolled into Chromium in http://crrev.com/132307

BUG=none
TEST=MSVC 2010 stops recompiling libjingle
TBR=sergeyu


Review URL: http://codereview.chromium.org/10021030

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@132649 0039d316-1c4b-4281-b951-d872f2087c98

yitian134/chromium,ropik/chromium,yitian134/chromium,ropik/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,ropik/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,adobe/chromium,adobe/chromium,adobe/chromium,adobe/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,ropik/chromium,yitian134/chromium,yitian134/chromium,yitian134/chromium,ropik/chromium